Base station apparatus for controlling downlink transmission power of a small-cell base station

A method for small-cell base station located in a macro cell, the small-cell base station having a small cell and in communication with a mobile station in a mobile communication network, the method comprising:

• acquiring information on electrical field intensity of a transmission signal transmitted from a macro-cell base station located at a periphery of the small-cell base station;
• and controlling a downlink transmission power of a downlink transmission signal in a range between a maximum power and a minimum power which are set in advance, including:
• in a state that the downlink transmission power is set to the maximum power and a function of suppressing interference between the small cell and the macro-cell is not operated, changing the downlink transmission power from the maximum power to the minimum power or stopping the transmission of the downlink transmission signal when the electric field intensity of the transmission signal from the macro-cell base station exceeds a preset electric-field upper threshold, or the electric field intensity is equal to or larger than the electric-field upper threshold;
• in a state that the downlink transmission power is set to the maximum power and the function of suppressing interference between the small cell and the macro cell is operated, maintaining the downlink transmission power at the maximum power regardless of whether the electric field intensity of transmission signal from the macro-cell base station exceeds the electric-field upper threshold, or the electric field intensity is equal to or larger than the electric-field upper threshold;
• and
• changing the downlink transmission power so as to return the downlink transmission power to the maximum power, when the electric field intensity of downlink signal from the macro-cell base station is smaller than a preset electric-field lower threshold.

A system for a small-cell base station located in a macro cell and in communication with a mobile station in a mobile communication network, the small-cell base station having a small cell and acquiring information on electrical field intensity of a transmission signal transmitted from a macro-cell base station located at a periphery of the small-cell base station, the system comprising:

• a control module to control a downlink transmission power of a downlink transmission signal in a range between a maximum power and a minimum power which are set in advance,
• wherein, in a state that the downlink transmission power is set to the maximum power and a function of suppressing interference between the small cell and the macro-cell is not operated, the control module controls changing the downlink transmission power from the maximum power to the minimum power or stopping the transmission of the downlink transmission signal when the electric field intensity of the transmission signal from the macro-cell base station exceeds a preset electric-field upper threshold, or the electric field intensity is equal to or larger than the electric-field upper threshold,
• wherein, in a state that the downlink transmission power is set to the maximum power and the function of suppressing interference between the small cell and the macro cell is operated, the control module controls maintaining the downlink transmission power at the maximum power regardless of whether the electric field intensity of transmission signal from the macro-cell base station exceeds the electric-field upper threshold, or the electric field intensity is equal to or larger than the electric-field upper threshold, and
• wherein, in a state that the downlink transmission power is set to the minimum power or the transmission of downlink transmission signal is stopped, the control module controls changing the downlink transmission power to return the downlink transmission power to the maximum power when the electric field intensity of the downlink signal from the macro-cell base station is smaller than a preset electric-field lower threshold.